Conventionally, a power conversion device (matrix converter) that uses a multiphase AC power source as an input and directly converts AC to AC has been known (mainly see Non Patent Literatures 1 and 2). Such a matrix converter, by turning ON/OFF a bidirectional switch that is connected to each phase of the multiphase AC power source as an input so as to switch a combination of two phases relating to interphase voltage to be outputted to a load side, outputs AC to the load side without converting the AC to DC. The matrix converter controls the switching of the bidirectional switch according to the voltage or frequency of the AC outputted to the load side.
Since the matrix converter directly converts AC to AC, the conversion loss of the matrix converter is smaller than the conversion loss of a power conversion device that uses an inverter that converts AC to DC and then converts the DC to AC again. In addition, since the matrix converter does not require an inverter circuit, the matrix converter is also excellent in miniaturization.